Mosquitoes increase disease risk in USA

By Doyle Rice, USA TODAY

Mosquitoes are more than just an annoyance for the itchy red bites they leave on our skin. They increasingly raise the prospect of spreading deadly diseases normally not found in the USA, experts warn.

By James Gathany,, CDC

Introducing new viruses: The Mid-Atlantic and South are most at risk from disease-carrying mosquitoes.

Introducing new viruses: The Mid-Atlantic and South are most at risk from disease-carrying mosquitoes.

The risks include dengue fever, usually found in South and Central America, the Caribbean, Southeast Asia and sub-Saharan Africa, but which was reported in Key West in May 2010, and in Hawaii earlier this year.

The USA is increasingly at risk from these and other diseases "as world travel increases, public health and control programs fail, and climate change alters mosquito ecology and habitats," cautions Laura Harrington, an entomologist at Cornell University in Ithaca, N.Y.

Mosquito-transmitted diseases, such as malaria and dengue, affect more than 350 million people worldwide each year, Harrington says, leading to more than 3 million deaths. There is no vaccine and no treatment for dengue.

Also, chikungunya (CHICK-en GUN-ya), a little-known but deadly mosquito-transmitted virus, has yet to hit the USA, but could soon make its way here from Africa and Asia, Harrington says.

Weather conditions can affect mosquito behavior

For mosquitoes, wetter is better, so eliminating standing water is the first step in mosquito control. Heavy rains after drought conditions and very high tides can also trigger mosquito blooms

Some species lay eggs in soil or sand and require water for hatching.

Mosquitoes are more active on full-moon nights when they
can see better.

Windy days and patio fans keep mosquitoes, which fly at only 1.0 to 1.5 miles per hour, at bay.

Susceptible to drying out, most mosquitoes spend sunny days in shady, humid locations.

Most mosquitoes
lay their eggs in water.

Source: Joe Conlon, American Mosquito Control Association

The threats are on the rise for the USA due to the introduction of the Asian tiger and African bush mosquitoes, which are transmitters of at least 22 different viruses that impact human health, including West Nile, dengue fever and encephalitis, she says.

Entomologists at Cornell are seeking funding from various federal agencies to help investigate new strategies to control diseases from mosquitoes. They're looking at ways to reduce egg production and curb the female mosquito's appetite for blood. Also, they're developing forecasting models to study how climate change will impact mosquito-borne diseases.

The parts of the country most at risk from disease-carrying mosquitoes, says Harrington, are the Mid-Atlantic and South.

"Once you get into the drier parts of the country, we don't see the species that are key to the transmission of these pathogens."

What's more, this week's intense heat and high humidity across the central and eastern USA is likely helping mosquitoes to breed, experts say, leading to what could be a banner late-summer for the outdoor pests.

Higher temperatures, coupled with rain, are the best weather conditions in which mosquitoes can breed, Harrington says.

But even in the absence of rain, humidity can also be helpful: "Humidity helps mosquitoes; it's better for their survival," Harrington says.

Additionally, Cornell-affiliated researchers warn that infestations of bedbugs, which also enjoy the warmth, tend to increase in the summertime. They're infesting homes, hotels, dorms, labs and airports worldwide.

Although they are not known to transmit any diseases to humans, "they play with our emotions," reports Jody Gangloff-Kaufmann, an urban entomologist with the New York State Integrated Pest Management Program in Babylon, N.Y. "The stress of dealing with them, and the depression and isolation that comes with them."

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